The invention relates to a method and apparatus as generally described hereinafter for controlling the combustion charge in internal combustion engines generally having externally supplied ignition.
In particular the invention is applicable to internal combustion engines with externally supplied ignition of various types, for instance 2-stroke Otto engines, 4-stroke Otto engines, multiple-fuel engines, piston engines, rotary-piston engines or the like. The invention can similarly be used not only in carburetor-type internal combustion engines but also in those provided with fuel injection or in butane gas or LPG engines with externally supplied ignition. The external ignition can preferably be effected by spark plugs, and in some cases by glow plugs as well.
As is well known, it is very important for the composition of the combustion charge which is to be combusted in a combustion chamber or chambers to be adapted as favorably as possible to given operating conditions. This combustion charge is a mixture of fuel and of gas which contains oxygen, in particular a fuel-air mixture; in many cases, the exhaust gas is added to this mixture to dilute the combustion charge. If the mixture is too rich for a given operating condition, the fuel consumption is unnecessarily high, and in such cases the emission of toxic exhaust gas components is also undesirably high. If the mixture (that is, the combustion charge) is set too lean, then once again the figures for the emission of toxic exhaust gas components increase, fuel consumption increases, and engine operation becomes faulty because of misfiring or retarded charge combustion. Numerous provisions are known for automatically adapting the combustion charge composition during operation to given operating conditions and also to conditions in the ambient atmosphere (such as air pressure, temperature and so forth). However, these provisions, if they are capable of favorably adapting the charge composition to prevailing operating parameters, are quite expensive and require numerous sensors and complicated systems for open- and closed-loop control.
The term "composition of the combustion charge" is intended to encompass both the case where the charge is formed outside the combustion chamber, whether with carburetors or by injection of fuel into the intake system, and the case where the charge is first formed in the combustion chamber by the injection of fuel into it.